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    SubjectRe: [PULL] cpumask: finally make them variable size w/ CPUMASK_OFFSTACK.
    On Wed, 09 May 2012 21:32:57 -0400, KOSAKI Motohiro <> wrote:
    > (5/9/12 2:10 AM), Rusty Russell wrote:
    > > Hi Ingo,
    > >
    > > I finally rebased this on top of your tip tree, and tested it
    > > locally. Some more old-style cpumask usages have crept in, but it's a
    > > fairly simple series.
    > >
    > > The final result is that if you enable CONFIG_CPUMASK_OFFSTACK, then
    > > 'struct cpumask' becomes an undefined type. You can't accidentally take
    > > the size of it, assign it, or pass it by value. And thus it's safe for
    > > us to make it smaller if nr_cpu_ids< NR_CPUS, as the final patch does.
    > >
    > > It unfortunately requires the lglock cleanup patch, which Al already has
    > > queued, so I've included it here.
    > Hi
    > Thanks this effort. This is very cleaner than I expected.
    > However I should NAK following one patch. sorry. because of, lru-drain is
    > called from memory reclaim context. It mean, additional allocation may not
    > work. Please just use bare NR_CPUS bitmap instead. space wasting is minor
    > issue than that.

    But if it fails the allocation, that's fine: we just send a few more
    IPIs to every CPU:

    + if (!zalloc_cpumask_var(&cpus_with_pcps, GFP_KERNEL)) {
    + on_each_cpu(drain_local_pages, NULL, 1);
    + return;
    + }

    We can do it the other way, but it sets a bad example, and after we get
    rid of cpumask, it becomes:

    static DECLARE_BITMAP(cpus_with_pcps, NR_CPUS);


    if (has_pcps)
    cpumask_set_cpu(cpu, to_cpumask(cpus_with_pcps));
    cpumask_clear_cpu(cpu, to_cpumask(cpus_with_pcps));
    on_each_cpu_mask(to_cpumask(cpus_with_pcps), drain_local_pages, NULL, 1);

    Or is there a reason we shouldn't even try to allocate here?


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      Last update: 2012-05-10 04:41    [W:0.050 / U:10.732 seconds]
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